1. Field of the Invention
This present invention generally relates to an antenna for wireless communication system, and more particularly to a surface-mountable dual-band monopole antenna for wireless local area network system which can be easily fabricated at a lower cost, has better antenna bandwidth and gain, and is adapted to operate in two separate bands.
2. Description of the Related Art
The construction of wireless local area network (WLAN) makes the integration of the signals and data from a variety of multimedia devices possible, and the connection among a plurality of devices is no more limited to the specific ports with wire transmission. In the meanwhile, in order to enhance the convenience and portability, xe2x80x9clight, thin, short, and smallxe2x80x9d have become the design standards of related components. The design of the antenna must conform to the aforementioned standards as well. In addition, whether an antenna can be assembled simply or not is also a big concern for antenna designing. With the rapid development in the surface mountable technique (SMT), the antenna applied to SMT can be assembled simply, and be packaged and connected at a lower cost. So, the surface-mountable antenna has attracted considerable attention. The conventional surface-mountable antenna is printed on the ceramic substrate, such as U.S. Pat. No. 5,668,557 issued to Kawahata on Jul. 16, 1997 entitled xe2x80x9cSurface-mount antenna and communication device using samexe2x80x9d which discloses a surface-mountable antenna, wherein the dielectric substrate thereof is made of a ceramic material. However, it is very difficult for the aforementioned antenna to obtain better antenna bandwidth and gain. Besides, the fabrication of the structure is quite difficult and complicated and the cost of the structure is high. Moreover, U.S. Pat. No. 6,100,849 issued to Tsubaki et al. on Aug. 8, 2000 entitled xe2x80x9cSurface mount antenna and communication apparatus using the samexe2x80x9d discloses a surface-mountable antenna of which the dielectric substrate is also made of a ceramic material. Compared with the aforementioned antenna, the fabrication of the antenna of Tsubaki et al. is easier. However, the ceramic material thereof is not only expensive but also fragile in the surface-mountable processes. In addition, the dielectric constant is relatively high, generally larger than 7, thereby significantly reducing the bandwidth and gain of the antenna as well as its competition with other products.
Moreover, the conventional antenna of the wireless network card equipped in a variety of electronic products can operate in a single band only. It can be expected that the performance and competitiveness of such an antenna will be inadequate for the prosperous market. So it will be the principal tendency to develop a dual-band antenna for applications in the wireless network cards.
Accordingly, it is necessary to provide an antenna for a wireless communication system which is surface mountable on the circuit board, and can be easily fabricated at a lower cost. The dielectric substrate thereof can provide better antenna bandwidth and gain, and the antenna can be adapted to operate in dual bands for wireless local area network (WLAN) operations.
It is a primary object of the present invention to provide a surface-mountable dual-band monopole antenna which is easily fabricated at a lower cost, and the dielectric substrate thereof can provide better antenna bandwidth and gain.
It is another object of the present invention to provide a surface-mountable dual-band monopole antenna adapted to operate in dual bands for WLAN operations.
To achieve the aforementioned objects, the present invention provides a surface-mountable dual-band monopole antenna comprising a substrate and a folded radiative metallic patch with a small metallic lug protruding outwardly from the substrate. A feeding point is located on the small metallic lug for transmitting the signals.
According to another aspect of the present invention, the folded radiative metallic patch encloses at least three surfaces of the substrate.
According to a further aspect of the present invention, the substrate is an air layer or it is made of the material of which dielectric constant is close to that of the air.
According to a still further aspect of the present invention, the substrate has a low rectangular-pillar profile.
According to a still further aspect of the present invention, the folded radiative metallic patch is folded from a planar metallic patch having a rectangular or substantially rectangular shape.
According to a still further aspect of the present invention, the planar metallic patch has at least one slot extending from one edge of the planar metallic patch to the interior of the planar metallic patch to constitute a first path and a second path on the planar metallic patch, wherein the first path is for the electric current path of the two operating frequencies of the surface-mountable dual-band monopole antenna and the second path is used to tune the impedance matching of the antenna.
According to a still further aspect of the present invention, the two operating frequencies comprise a higher frequency and a lower one which are the first two resonant frequencies of the surface-mountable dual-band monopole antenna.
According to a still further aspect of the present invention, the first path has a starting point and an end point. The starting point is the feeding point of surface-mountable dual-band monopole antenna, and the first path has a turn of 180xc2x0 or substantially 180xc2x0 to enable the end point to extend towards the direction of the starting point.